具体实施方式：
[0020]The term “collagen” refers to any one of the known collagen types, including collagen types I through XX, as well as to any other collagens, whether natural, synthetic, semi-synthetic, or recombinant. It includes all of the collagens, modified collagens and collagen-like proteins described herein. The term also encompasses procollagens and collagen-like proteins or collagenous proteins comprising the motif (Gly-X-Y)n where n is an integer. It encompasses molecules of collagen and collagen-like proteins, trimers of collagen molecules, fibrils of collagen, and fibers of collagen fibrils. It also refers to chemically, enzymatically or recombinantly-modified collagens or collagen-like molecules that can be fibrillated as well as fragments of collagen, collagen-like molecules and collagenous molecules capable of assembling into a nanofiber.
[0021]In some embodiments, amino acid residues, such as lysine and proline, in a collagen or collagen-like protein may lack hydroxylation or may have a lesser or greater degree of hydroxylation than a corresponding natural or unmodified collagen or collagen-like protein. In other embodiments, amino acid residues in a collagen or collagen-like protein may lack glycosylation or may have a lesser or greater degree of glycosylation than a corresponding natural or unmodified collagen or collagen-like protein.
[0022]The collagen in a collagen composition may homogenously contain a single type of collagen molecule, such as 100% bovine Type I collagen or 100% Type III bovine collagen, or may contain a mixture of different kinds of collagen molecules or collagen-like molecules, such as a mixture of bovine Type I and Type III molecules. Such mixtures may include >0%, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 99 or <100% of the individual collagen or collagen-like protein components. This range includes all intermediate values. For example, a collagen composition may contain 30% Type I collagen and 70% Type III collagen, or may contain 33.3% of Type I collagen, 33.3% of Type II collagen, and 33.3% of Type III collagen, where the percentage of collagen is based on the total mass of collagen in the composition or on the molecular percentages of collagen molecules.
[0023]“Collagen fibrils” are nanofibers composed of tropocollagen (triple helices of collagen molecules). Tropocollagens also include tropocollagen-like structures exhibiting triple helical structures. The collagen fibrils of the invention may have diameters ranging from 1 nm and 1 μm. For example, the collagen fibrils of the invention may have an average or individual fibril diameter ranging from 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1,000 nm (1 μm). This range includes all intermediate values and subranges. In some of the embodiments of the invention collagen fibrils will form networks. Collagen fibrils can associate into fibrils exhibiting a banded pattern and these fibrils can associate into larger aggregates of fibrils. In some embodiments the collagen or collagen-like fibrils will have diameters and orientations similar to those in the top grain or surface layer of a bovine or other conventional leather. In other embodiments, the collagen fibrils may have diameters comprising the top grain and those of a corium layer of a conventional leather.
[0024]A “collagen fiber” is composed of collagen fibrils that are tightly packed and exhibit a high degree of alignment in the direction of the fiber. It can vary in diameter from more than 1 μm to more than 10 μm, for example >1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 μm or more. Some embodiments of the network of collage fibrils of the invention do not contain substantial content of collagen fibers having diameters greater than 5 μm. The composition of the grain surface of a leather can differ from its more internal portions, such as the corium which contains coarser fiber bundles.
[0025]“Fibrillation” refers to a process of producing collagen fibrils. It may be performed by raising the pH or by adjusting the salt concentration of a collagen solution or suspension. In forming the fibrillated collagen, the collagen may be incubated to form the fibrils for any appropriate length of time, including between 1 min and 24 hrs and all intermediate values.
[0026]The fibrillated collagen described herein may generally be formed in any appropriate shape and/or thickness, including flat sheets, curved shapes/sheets, cylinders, threads, and complex shapes. These sheets and other forms may have virtually any linear dimensions including a thickness, width or height greater of 10, 20, 30, 40, 50, 60, 70,80, 90 mm; 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 50, 100, 200, 500, 1,000, 1,500, 2,000 cm or more.
[0027]The fibrillated collagen may lack any or any substantial amount of higher order structure. In a preferred embodiment, the collagen fibrils will be unbundled and not form the large collagen fibers found in animal skin and provide a strong and uniform non-anisotropic structure to the biofabricated leather.
[0028]In other embodiments, some collagen fibrils can be bundled or aligned into higher order structures. Collagen fibrils in a biofabricated leather may exhibit an orientation index ranging from 0, >0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, <1.0, or 1.0, wherein an orientation index of 0 describes collagen fibrils that lack alignment with other fibrils and an orientation index of 1.0 describes collagen fibrils that are completely aligned. This range includes all intermediate values and subranges. Those of skill in the art are familiar with the orientation index which is also incorporated by reference to Sizeland, et al., J. Agric. Food Chem. 61: 887-892 (2013) or Basil-Jones, et al., J. Agric. Food Chem. 59: 9972-9979 (2011).
[0029]A biofabricated leather may be fibrillated and processed to contain collagen fibrils that resemble or mimic the properties of collagen fibrils produced by particular species or breeds of animals or by animals raised under particular conditions.
[0030]Alternatively, fibrillation and processing conditions can be selected to provide collagen fibrils distinct from those found in nature, such as by decreasing or increasing the fibril diameter, degree of alignment, or degree of crosslinking compared to fibrils in natural leather.
[0031]A crosslinked network of collagen, sometimes called a hydrogel, may be formed as the collagen is fibrillated, or it may form a network after fibrillation; in some variations, the process of fibrillating the collagen also forms gel-like network. Once formed, the fibrillated collagen network may be further stabilized by incorporating molecules with di-, tri-, or multifunctional reactive groups that include chromium, amines, carboxylic acids, sulfates, sulfites, sulfonates, aldehydes, hydrazides, sulfhydryls, diazarines, aryl azides, acrylates, epoxides, or phenols.
[0032]The fibrillated collagen network may also be polymerized with other agents (e.g. polymers that are capable of polymerizing or other suitable fibers), which could be used to further stabilize the matrix and provide the desired end structure. Hydrogels based upon acrylamides, acrylic acids, and their salts may be prepared using inverse suspension polymerization. Hydrogels described herein may be prepared from polar monomers. The hydrogels used may be natural polymer hydrogels, synthetic polymer hydrogels, or a combination of the two. The hydrogels used may be obtained using graft polymerization, crosslinking polymerization, networks formed of water soluble polymers, radiation crosslinking, and so on. A small amount of crosslinking agent may be added to the hydrogel composition to enhance polymerization.
[0033]Average or individual collagen fibril length may range from 100, 200, 300, 400, 500, 600, 700, 800, 900, 1,000 (1 μm); 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1,000 μm (1 mm) throughout the entire thickness of a biofabricated leather. These ranges include all intermediate values and subranges.
[0034]Fibrils may align with other fibrils over 50, 100, 200, 300, 400, 500 μm or more of their lengths or may exhibit little or no alignment. In other embodiments, some collagen fibrils can be bundled or aligned into higher order structures.
[0035]Collagen fibrils in a biofabricated leather may exhibit an orientation index ranging from 0, >0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, <1.0, or 1.0, wherein an orientation index of 0 describes collagen fibrils that lack alignment with other fibrils and an orientation index of 1.0 describes collagen fibrils that are completely aligned. This range includes all intermediate values and subranges. Those of skill in the art are familiar with the orientation index which is also incorporated by reference to Sizeland, et al., J. Agric. Food Chem. 61: 887-892 (2013) or Basil-Jones, et al., J. Agric. Food Chem. 59: 9972-9979 (2011).
[0036]Collagen fibril density of a biofabricated leather may range from about 1 to 1,000 mg/cc, preferably from 5 to 500 mg/cc including all intermediate values, such as 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900 and 1,000 mg/cc.
[0037]The collagen fibrils in a biofabricated leather may exhibit a unimodal, bimodal, trimodal, or multimodal distribution, for example, a biofabricated leather may be composed of two different fibril preparations each having a different range of fibril diameters arranged around one of two different modes. Such mixtures may be selected to impart additive, synergistic or a balance of physical properties on a biofabricated leather conferred by fibrils having different diameters.
[0038]Natural leather products may contain 150-300 mg/cc collagen based on the weight of the leather product. A biofabricated leather may contain a similar content of collagen or collagen fibrils as conventional leather based on the weight of the biofabricated leather, such as a collagen concentration of 100, 150, 200, 250, 300 or 350 mg/cc.
[0039]The fibrillated collagen, sometimes called a hydrogel, may have a thickness selected based on its ultimate use. Thicker or more concentrated preparations of the fibrillated collagen generally produce thicker biofabricated leathers. The final thickness of a biofabricated leather may be only 10, 20, 30, 40, 50, 60, 70, 80 or 90% that of the fibril preparation prior to shrinkage caused by crosslinking, dehydration and lubrication.
[0040]“Crosslinking” refers to formation (or reformation) of chemical bonds within between collagen molecules. A crosslinking reaction stabilizes the collagen structure and in some cases forms a network between collagen molecules. Any suitable crosslinking agent known in the art can be used including, without limitation, mineral salts such as those based on chromium, formaldehyde, hexamethylene diisocyanate, glutaraldehyde, polyepoxy compounds, gamma irradiation, and ultraviolet irradiation with riboflavin. The crosslinking can be performed by any known method; see, e.g., Bailey et al., Radiat. Res. 22:606-621 (1964); Housley et al., Biochem. Biophys. Res. Commun. 67:824-830 (1975); Siegel, Proc. Natl. Acad. Sci. U.S.A. 71:4826-4830 (1974); Mechanic et al., Biochem. Biophys. Res. Commun. 45:644-653 (1971); Mechanic et al., Biochem. Biophys. Res. Commun. 41:1597-1604 (1970); and Shoshan et al., Biochim. Biophys. Acta 154:261-263 (1968) each of which is incorporated by reference.
[0041]Crosslinkers include isocyantes, carbodiimide, poly(aldehyde), poly(azyridine), mineral salts, poly(epoxies), enzymes, thiirane, phenolics, novolac, resole as well as other compounds that have chemistries that react with amino acid side chains such as lysine, arginine, aspartic acid, glutamic acid, hydroxylproline, or hydroxylysine.
[0042]A collagen or collagen-like protein may be chemically modified to promote chemical and/or physical crosslinking between the collagen fibrils. Chemical crosslinking may be possible because reactive groups such as lysine, glutamic acid, and hydroxyl groups on the collagen molecule project from collagen's rod-like fibril structure. Crosslinking that involve these groups prevent the collagen molecules from sliding past each other under stress and thus increases the mechanical strength of the collagen fibers. Examples of chemical crosslinking reactions include but are not limited to reactions with the ϵ-amino group of lysine, or reaction with carboxyl groups of the collagen molecule. Enzymes such as transglutaminase may also be used to generate crosslinks between glutamic acid and lysine to form a stable γ-glutamyl-lysine crosslink. Inducing crosslinking between functional groups of neighboring collagen molecules is known in the art. Crosslinking is another step that can be implemented here to adjust the physical properties obtained from the fibrillated collagen hydrogel-derived materials.
[0043]Still fibrillating or fibrillated collagen may be crosslinked or lubricated. Collagen fibrils can be treated with compounds containing chromium or at least one aldehyde group, or vegetable tannins prior to network formation, during network formation, or network gel formation. Crosslinking further stabilizes the fibrillated collagen leather. For example, collagen fibrils pre-treated with acrylic polymer followed by treatment with a vegetable tannin, such as Acacia Mollissima, can exhibit increased hydrothermal stability. In other embodiments, glyceraldehyde may be used as a cross-linking agent to increase the thermal stability, proteolytic resistance, and mechanical characteristics, such as Young's modulus and tensile stress, of the fibrillated collagen.
[0044]A biofabricated material containing a network of collagen fibrils may contain 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20% or more of a crosslinking agent including tanning agents used for conventional leather. The crosslinking agents may be covalently bound to the collagen fibrils or other components of a biofabricated material or non-covalently associated with them. Preferably, a biofabricated leather will contain no more than 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10% of a crosslinking agent.
[0045]“Lubricating” describes a process of applying a lubricant, such as a fat or other hydrophobic compound or any material that modulates or controls fibril-fibril bonding during dehydration to leather or to biofabricated products comprising collagen. A desirable feature of the leather aesthetic is the stiffness or hand of the material. In order to achieve this property, water-mediated hydrogen bonding between fibrils and/or fibers is limited in leather through the use of lubricants. Examples of lubricants include fats, biological, mineral or synthetic oils, cod oil, sulfonated oil, polymers, organofunctional siloxanes, and other hydrophobic compounds or agents used for fatliquoring conventional leather as well as mixtures thereof. While lubricating is in some ways analogous to fatliquoring a natural leather, a biofabricated product can be more uniformly treated with a lubricant due to its method of manufacture, more homogenous composition and less complex composition.
[0046]Other lubricants include surfactants, anionic surfactants, cationic surfactants, cationic polymeric surfactants, anionic polymeric surfactants, amphiphilic polymers, fatty acids, modified fatty acids, nonionic hydrophilic polymers, nonionic hydrophobic polymers, poly acrylic acids, poly methacrylic, acrylics, natural rubbers, synthetic rubbers, resins, amphiphilic anionic polymer and copolymers, amphiphilic cationic polymer and copolymers and mixtures thereof as well as emulsions or suspensions of these in water, alcohol, ketones, and other solvents.
[0047]Lubricants may be added to a biofabricated material containing collagen fibrils. Lubricants may be incorporated in any amount that facilitates fibril movement or that confers leather-like properties such as flexibility, decrease in brittleness, durability, or water resistance. A lubricant content can range from about 0.1, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60% by weight of the biofabricated leather.
[0048]Other additives may be added to modify the properties of biofabricated leather or material. Suitable additives include but are not limited to dyes, pigments, fragrances, resins, textile binders and microparticles. Resins may be added to modify the stretchability, strength, and softness of the material. Suitable resins include but are not limited to elastomers, acrylic copolymers, polyurethane, and the like. Suitable elastomers include but are not limited to styrene, isoprene, butadiene copolymers such as KRAYTON® elastomers, Hycar® acrylic resins. Resins may be used at from about 5% to 200%, or from about 50% to 150% (based on the weight of collagen).
[0049]“Dehydrating” or “dewatering” describes a process of removing water from a mixture containing collagen fibrils and water, such as an aqueous solution, suspension, gel, or hydrogel containing fibrillated collagen. Water may be removed by filtration, evaporation, freeze-drying, solvent exchange, vacuum-drying, convection-drying, heating, irradiating or microwaving, or by other known methods for removing water. In addition, chemical crosslinking of collagen is known to remove bound water from collagen by consuming hydrophilic amino acid residues such as lysine, arginine, and hydroxylysine among others. The inventors have found that acetone quickly dehydrates collagen fibrils and may also remove water bound to hydrated collagen molecules. Water content of a biofabricated material or leather after dehydration is preferably no more than 60% by weight, for example, no more than 5, 10, 15, 20, 30, 35, 40, 50 or 60% by weight of the biofabricated leather. This range includes all intermediate values. Water content is measured by equilibration at 65% relative humidity at 25° C. and 1 atm.
[0050]“Grain texture” describes a leather-like texture which is aesthetically or texturally the similar to the texture of a full grain leather, top grain leather, corrected grain leather (where an artificial grain has been applied), or coarser split grain leather texture. Advantageously, the biofabricated material of the invention can be tuned to provide a fine grain, resembling the surface grain of a leather.
[0051]The articles in the invention may include foot wear, garments, gloves, furniture or vehicle upholstery, jewelry and other leather goods and products. It includes but is not limited to clothing, such as overcoats, coats, jackets, shirts, trousers, pants, shorts, swimwear, undergarments, uniforms, emblems or letters, costumes, ties, skirts, dresses, blouses, leggings, gloves, mittens, shoes, shoe components such as sole, quarter, tongue, cuff, welt, and counter, dress shoes, athletic shoes, running shoes, casual shoes, athletic, running or casual shoe components such as toe cap, toe box, outsole, midsole, upper, laces, eyelets, collar, lining, Achilles notch, heel, and counter, fashion or women's shoes and their shoe components such as upper, outer sole, toe spring, toe box, decoration, vamp, lining, sock, insole, platform, counter, and heel or high heel, boots, sandals, buttons, sandals, hats, masks, headgear, headbands, head wraps, and belts; jewelry such as bracelets, watch bands, and necklaces; gloves, umbrellas, walking sticks, wallets, mobile phone or wearable computer coverings, purses, backpacks, suitcases, handbags, folios, folders, boxes, and other personal objects; athletic, sports, hunting or recreational gear such as harnesses, bridles, reins, bits, leashes, mitts, tennis rackets, golf clubs, polo, hockey, or lacrosse gear, chessboards and game boards, medicine balls, kick balls, baseballs, and other kinds of balls, and toys; book bindings, book covers, picture frames or artwork; furniture and home, office or other interior or exterior furnishings including chairs, sofas, doors, seats, ottomans, room dividers, coasters, mouse pads, desk blotters, or other pads, tables, beds, floor, wall or ceiling coverings, flooring; automobile, boat, aircraft and other vehicular products including seats, headrests, upholstery, paneling, steering wheel, joystick or control coverings and other wraps or coverings.
[0052]Physical Properties of a biofabricated network of collagen fibrils or a biofabricated leather may be selected or tuned by selecting the type of collagen, the amount of concentration of collagen fibrillated, the degree of fibrillation, crosslinking, dehydration and lubrication.
[0053]Many advantageous properties are associated with the network structure of the collagen fibrils which can provide strong, flexible and substantially uniform properties to the resulting biofabricated material or leather. Preferable physical properties of the biofabricated leather according to the invention include a tensile strength ranging from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more MPa, a flexibility determined by elongation at break ranging from 1, 5, 10, 15, 20, 25, 30% or more, softness as determined by ISO 17235 of 4, 5, 6, 7, 8 mm or more, a thickness ranging from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3. 1,4, 1,5, 1.6, 1.7, 1.8, 1.9, 2.0 mm or more, and a collagen density (collagen fibril density) of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1,000 mg/cc or more, preferably 100-500 mg/cc. The above ranges include all subranges and intermediate values.
[0054]Thickness. Depending on its ultimate application a biofabricated material or leather may have any thickness. Its thickness preferably ranges from about 0.05 mm to 20 mm as well as any intermediate value within this range, such as 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 40, 50 mm or more. The thickness of a biofabricated leather can be controlled by adjusting collagen content.
[0055]Elastic modulus. The elastic modulus (also known as Young's modulus) is a number that measures an object or substance's resistance to being deformed elastically (i.e., non-permanently) when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region. A stiffer material will have a higher elastic modulus. The elastic modulus can be measured using a texture analyzer.
[0056]A biofabricated leather can have an elastic modulus of at least 100 kPa. It can range from 100 kPa to 1,000 MPa as well as any intermediate value in this range, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1,000 MPa. A biofabricated leather may be able to elongate up to 300% from its relaxed state length, for example, by >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, or 300% of its relaxed state length.
[0057]Tensile strength (also known as ultimate tensile strength) is the capacity of a material or structure to withstand loads tending to elongate, as opposed to compressive strength, which withstands loads tending to reduce size. Tensile strength resists tension or being pulled apart, whereas compressive strength resists compression or being pushed together.
[0058]A sample of a biofabricated material may be tested for tensile strength using an Instron machine. Clamps are attached to the ends of the sample and the sample is pulled in opposite directions until failure. Good strength is demonstrated when the sample has a tensile strength of at least 1 MPa. A biofabricated leather can have a tensile strength of at least 1 kPa. It can range from 1 kPa to 100 MPa as well as any intermediate value in this range, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 50, 100, 200, 300, 400, 500 kPA; 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 MPa.
[0059]Tear strength (also known as tear resistance) is a measure of how well a material can withstand the effects of tearing. More specifically however it is how well a material (normally rubber) resists the growth of any cuts when under tension, it is usually measured in kN/m. Tear resistance can be measured by the ASTM D 412 method (the same used to measure tensile strength, modulus and elongation). ASTM D 624 can be used to measure the resistance to the formation of a tear (tear initiation) and the resistance to the expansion of a tear (tear propagation). Regardless of which of these two is being measured, the sample is held between two holders and a uniform pulling force applied until the aforementioned deformation occurs. Tear resistance is then calculated by dividing the force applied by the thickness of the material. A biofabricated leather may exhibit tear resistance of at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 150 or 200% more than that of a conventional top grain or other leather of the same thickness comprising the same type of collagen, e.g., bovine Type I or Type III collagen, processed using the same crosslinker(s) or lubricants. A biofabricated material may have a tear strength ranging from about 1 to 500 N, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, or 500 as well as any intermediate tear strength within this range.
[0060]Softness. ISO 17235:2015 specifies a non-destructive method for determining the softness of leather. It is applicable to all non-rigid leathers, e.g. shoe upper leather, upholstery leather, leather goods leather, and apparel leather. A biofabricated leather may have a softness as determined by ISO 17235 of 2, 3, 4, 5, 6, 7, 8, 10, 11, 12 mm or more.
[0061]Grain. The top grain surface of leather is often regarded as the most desirable due to its soft texture and smooth surface. The top grain is a highly porous network of collagen fibrils. The strength and tear resistance of the grain is often a limitation for practical applications of the top grain alone and conventional leather products are often backed with corium having a much coarser grain. A biofabricated material as disclosed herein which can be produced with strong and uniform physical properties or increased thickness can be used to provide top grain like products without the requirement for corium backing.
[0062]Content of other components. In some embodiments, the collagen is free of other leather components such as elastin or non-structural animal proteins. However, in some embodiments the content of actin, keratin, elastin, fibrin, albumin, globulin, mucin, mucinoids, noncollagen structural proteins, and/or noncollagen nonstructural proteins in a biofabricated leather may range from 0, 1, 2, 3,4, 5, 6, 7, 8, 9 to 10% by weight of the biofabricated leather. In other embodiments, a content of actin, keratin, elastin, fibrin, albumin, globulin, mucin, mucinoids, noncollagen structural proteins, and/or noncollagen nonstructural proteins may be incorporated into a biofabricated leather in amounts ranging from >0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20% or more by weight of a biofabricated leather. Such components may be introduced during or after fibrillation, cross-linking, dehydration or lubrication.
[0063]A “leather dye” refers to dyes which can be used to color leather or biofabricated leather. These include acidic dyes, direct dyes, lakes, sulfur dyes, basic dyes and reactive dyes. Dyes and pigments can also be incorporated into a precursor of a biofabricated leather, such as into a suspension or network gel comprising collagen fibrils during production of the biofabricated leather.
[0064]“Fillers”. In some embodiments a biofabricated leather may comprise fillers, other than components of leather, such as microspheres. One way to control the organization of the dehydrated fibril network is to include filling materials that keep the fibrils spaced apart during dehydration. These filler materials include nanoparticles, microparticles, or various polymers such as syntans commonly used in the tanning industry. These filling materials could be part of the final dehydrated leather material, or the filling materials could be sacrificial, that is they are degraded or dissolved away leaving open space for a more porous fibril network. The shape and dimension of these fillers may also be used to control the orientation of the dehydrated fibril network.
[0065]In some embodiments a filler may comprise polymeric microsphere(s), bead(s), fiber(s), wire(s), or organic salt(s). Other materials may also be embedded or otherwise incorporated into a biofabricated leather or into a network of collagen fibrils according to the invention. These include, but are not limited to one fibers, including both woven and nonwoven fibers as well as cotton, wool, cashmere, angora, linen, bamboo, bast, hemp, soya, seacell, fibers produced from milk or milk proteins, silk, spider silk, other peptides or polypeptides including recombinantly produced peptides or polypeptides, chitosan, mycelium, cellulose including bacterial cellulose, wood including wood fibers, rayon, lyocell, vicose, antimicrobial yarn (A.M.Y.), Sorbtek, nylon, polyester, elastomers such as lycra®, spandex or elastane and other polyester-polyurethane copolymers, aramids, carbon including carbon fibers and fullerenes, glass including glass fibers and nonwovens, silicon and silicon-containing compounds, minerals, including mineral particles and mineral fibers, and metals or metal alloys, including those comprising iron, steel, lead, gold, silver, platinum, copper, zinc and titanium, which may be in the form of particles, fibers, wires or other forms suitable for incorporating into biofabricated leather. Such fillers may include an electrically conductive material, magnetic material, fluorescent material, bioluminescent material, phosphorescent material or other photoluminescent material, or combinations thereof. Mixtures or blends of these components may also be embedded or incorporated into a biofabricated leather, for example, to modify the chemical and physical properties disclosed herein.
[0066]Various forms of collagen are found throughout the animal kingdom. The collagen used herein may be obtained from animal sources, including both vertebrates and invertebrates, or from synthetic sources. Collagen may also be sourced from byproducts of existing animal processing. Collagen obtained from animal sources may be isolated using standard laboratory techniques known in the art, for example, Silva et. Al., Marine Origin Collagens and its Potential Applications, Mar. Drugs, 2014 December, 12(12); 5881-5901).
[0067]The collagen described herein also may be obtained by cell culture techniques including from cells grown in a bioreactor.
[0068]Collagen may also be obtained via recombinant DNA techniques. Constructs encoding non-human collagen may be introduced into host organisms to produce non-human collagen. For instance, collagen may also be produced with yeast, such as Hansenula polymorphs, Saccharomyces cerevisiae, Pichia pastoris and the like as the host. Further, in recent years, bacterial genomes have been identified that provide the signature (Gly-Xaa-Yaa)n repeating amino acid sequence that is characteristic of triple helix collagen. For example, gram positive bacterium Streptococcus pyogenes contains two collagen-like proteins, Scl1 and Sc12 that now have well characterized structure and functional properties. Thus, it would be possible to obtain constructs in recombinant E. coli systems with various sequence modifications of either Scl1 or Scl2 for establishing large scale production methods. Collagen may also be obtained through standard peptide synthesis techniques. Collagen obtained from any of the techniques mentioned may be further polymerized. Collagen dimers and trimers are formed from self-association of collagen monomers in solution.
[0069]Materials that are useful in the present invention include but are not limited to biofabricated leather materials natural or synthetic woven fabrics, non-woven fabrics, knitted fabrics, mesh fabrics, and spacer fabrics.
[0070]Any material that retains the collagen fibrils can be useful in the present invention. In general, fabrics that are useful have a mesh ranging from 300 threads per square inch to 1 thread per square foot or a pore size greater than or equal to about 11 μm in diameter. Spu